77-GHz FOWLP MIMO AiP for Compact High-Resolution Radar With Horizontally and Vertically Long- and Medium-Range Sensing

77-GHz automotive multiple input multiple output (MIMO) radar is traditionally implemented in the bulky PCB board in a cascaded format to achieve a high resolution. This article reports mold-on-mold fan-out wafer-level packaging (FOWLP) antenna-in-packages (AiP) technology to directly mold the radar dies into the package while with the mold-on-mold advantage of integrating the antenna seamlessly on the top of the package. This process combined with the patented MIMO layout makes a high-resolution MIMO radar achievable in a very compact format: within a space of 64 x 32 x 0.7 mm, two 32 x 16 mm AiPs and two 16 x 16 mm AiPs, with each AiP carrying one transceiver die, are configured to achieve both long range radar (LRR) and medium range radar (MRR) functions with 1 degrees angular resolution in both vertical and horizontal sensing operations. We disclose the FOWLP AiP structure and key design details to implement such a MIMO radar, including AiP element and RF passive circuits modeling and test; the MIMO AiP performance is shown in terms of impedance bandwidth, patterns, feed line consistency, and isolations; the LRR and MRR MIMO detection range and resolution performance are finally evaluated.